1. Field of the Invention
The invention relates to a device for laterally aligning sheets in a feeder of a sheet-fed rotary printing press and, more particularly, such a printing press wherein sheets having respective leading edges aligned at front lays of a feeder table are gripped by a gripper system of a pregripper in succession individually at an edge region thereof, and transferred with a swivelling or revolving movement to a gripper system of a revolvingly driven feed cylinder
2. Description of the Related Art
A device of this general type has become known heretofore from the published, non-prosecuted European Patent Application 0 120 348, wherein an aligning cylinder is disposed between the feeder table and a pregripper cylinder to which the sheet to be aligned is fed over the feeder table. At least two rows of front lays are disposed in the aligning cylinder symmetrically with the circumference thereof and have pull strips assigned for aligning the lateral edges of the sheets, the sheets being guided by grippers until the sheets are taken over in-register by a farther-guiding transporter The necessary leading-edge alignment as well as the tight gripping of the sheet during the lateral alignment thereof increases the alignment accuracy. When the sheets are shingled or stream-fed, a reduction in the shingle spacing or overlap is allowed or enabled The technical expense or effort required for achieving this advantage is very great, however.
An electronic device for controlling the position of the sheets on the cylinder of a printing press is disclosed in the published German Patent Document DE 41 13 478 A1. Scanning elements of CCD lines and a light source determine the position of the leading edge of the sheet in order to ensure an in-register sheet transfer. Mainly bent or creased leading edges of sheets are supposed to be detected thereby so as to correct possible errors by varying the printing parameters. This heretofore known publication mentions that, by this control of the sheet position, it is possible to hold the leading edge of the sheet in the gripper system of every printing unit so as to detect position variations during sheet transfer between the printing units or within a respective printing unit.